A vibrating gyroscope is used, for example, in an image compensation unit of a camcorder, or in a location control unit of a car navigation system. One method to get more exact information is to improve the linearity of the output signal from the vibrating gyroscope.
A conventional vibrating unit 20 used in a vibrating gyroscope, as shown in FIG. 1, is usually formed as a triangular prism. The vibrating unit 20 comprises a regular triangular prism-shaped vibrating body 21 with three mono-crystalline and piezoelectric elements 22, 23, and 24 attached on each of three sides of the vibrating body 21, respectively.
In FIG. 1, the vibrating unit 20 is located in a coordinate system that has the origin O on the central axis of the vibrating unit 20, which is coincided with X-axis. The XY-plane of the coordinate system is parallel with the third piezoelectric element 24 and the Z-axis extends perpendicular to the third piezoelectric element 24. The terminology "reference vibration" means vibration in the Z-axis direction in the vibrating body 21 when oscillated by first and second piezoelectric elements 22 and 23 at a constant frequency, while the terminology "cross vibration" means vibration in the Y-axis direction, for example, caused by a Coriolis force that is induced from an angular velocity externally exerted on the vibrating body 21 about the X-axis.
As shown in FIG. 4, a conventional detector for detecting an exciting force in a vibrating gyroscope that has a vibrating unit 20 includes a differential amplifier 30 and a direct current amplifier 40. The differential amplifier 30 differentially amplifies two signals from first and second piezoelectric elements 22 and 23 generated by a composite vibration that includes a reference vibration and cross vibration components.
The oscillating unit 10 provides oscillating energy in the Z-axis direction at a constant frequency through input lines 11 and 12 to the first and second sides of the vibrating body 21. The oscillating energy generates a reference vibration of the vibrating body 21. The third piezoelectric element 24 transforms such vibration into electricity, and then such electricity is used as a feedback signal 13 to the oscillating unit 10. If an angular velocity about X-axis is externally exerted to the vibrating body 21, the Coriolis force created in the vibrating body 21 generates a cross vibration in the Y-axis direction. The cross vibration and the reference vibration produce a composite vibration. The composite vibration is transformed into piezoelectric voltages by the first and second piezoelectric elements 22 and 23. Two piezoelectric voltages are differentially amplified by the differential amplifier 30 to produce a signal corresponding to a difference between one piezoelectric voltage by the first piezoelectric element 22 and the other piezoelectric voltage by the second piezoelectric element 23. If no angular velocity is applied to the vibrating body 21, the output signal of the differential amplifier 30 may be `zero`. The output signal of the differential amplifier 30 is further amplified by a direct current amplifier 40, and then is supplied to a display 50 as a signal representing the angular velocity.
The conventional detector for detecting an exciting force in a vibrating gyroscope has some shortcomings. The vibration body may be under a composite vibration having both a reference vibration component and a cross vibration component. That is, the vibration body may vibrate in a direction other than the direction of the reference vibration and at a frequency other than the constant frequency. Thus, the phase and intensity of the composite vibration is varied non-linearly, which results in a signal obtained from the output unit that is not linear.